Polyphenylene ether polymers and resins are characterized by a unique combination of chemical, physical and electrical properties over a temperature range of more than 600.degree. F., extending from a brittle point of about -275.degree. F. to a heat distortion temperature of about 375.degree. F. This combination of properties renders the polyphenylene ethers suitable for a broad range of applications. However, the usefulness of the polyphenylene ethers alone is limited owing to their poor processibility, impact resistance and chemical resistance.
Accordingly, polyphenylene ether polymers are often blended with one or more additional polymers to improve processibility, impact resistance, and/or chemical resistance. The Finholt U.S. Pat. No. 3,379,792 discloses blends of polyphenylene ether resins with a polyamide in order to improve the processibility of the polyphenylene ether resins. Typical polyamides for use in combination with polyphenylene ethers include nylon 6 and nylon 6,6. However, articles molded from such blend compositions often change dimensions as they gain or lose moisture. The moisture-related dimensional instability results from the addition of the nylon components. In the past, moisture-related dimensional instability caused by the nylon components has been reduced by using additives such as phenols. However, the phenolic additives also tend to reduce the melting points of the nylon components, whereby the desirable reduction in moisture-related dimensional instability is accompanied by an undesirable reduction in the heat deflection temperature of the blend compositions.
Blend compositions of polyphenylene ethers and nylon polyamides also exhibit a degree of dimensional instability caused by thermal expansions and contractions. The thermal-related dimensional instability results from the high coefficients of thermal expansion of the nylon polyamides relative to polyphenylene ethers. In the past, fillers of glass and/or minerals have been added to the compositions in order to reduce the thermal-related dimensional instability of these compositions. However, such fillers also reduce impact properties and the quality of the surface appearance of molded articles.
Thus, a need exists for blends of polyphenylene ether and polyamide which exhibit reductions in moisture-related and/or thermal-related dimensional instability, particularly without compromising other advantageous properties of such compositions.
The inclusion of a compatibilizer in blends of polyphenylene ethers and polyamides in order to improve the compatibility of these two polymer components is known. Suitable compatibilizers are disclosed, for example, in the Ueno et al U.S. Pat. No. 4,315,086, the Gallucci et al U.S. Pat. No. 4,873,286 and the Gianchandai et al U.S. Pat. No. 4,997,612.